Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (ℓ.63-65).

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 273-275).

Increasing popularity of offsite modular construction has increased demand for transportation of very large (1000-3000 tonne) indivisible loads. Crossing poor soils presents a serious risk of ground failure, particularly as larger vehicles’ greater influence depths produce a very different soil response to conventional vehicles. Temporary haul roads designed conventionally may be excessively conservative and unaffordable as a temporary asset; cost reduction through observational risk management is sought. This thesis experimentally investigates soft silt and clay soils through cyclic triaxial testing. Particular focus is given to anisotropically normally consolidated silt, carefully manufactured through slurry consolidation to replicate liquefiable fabric. Soil samples are tested under the unusual loading conditions associated with heavy haul roads (slow, large-strain, infrequent). A new design approach for temporary heavy haul roads is demonstrated: cyclic traffic load can be used to improve soil, either by gradually rearranging fabric (medium-strain treatment) or remoulding and consolidating excess pore water pressure (large-strain treatment). Liquefiable silt benefits from both, plastic clay only from the latter. These findings, combined with a robust monitoring regime and management of heavy traffic, could be used to improve soil strength over time during operations. This could realise significant project savings and increase viability of modular construction.

This study focused on the correlation between the primary and the secondary impacts of a road development. Its methodology is aimed at coupling the conventional cost benefit analysis with an economic impact analysis. The secondary impacts of road development concentrated on the changes in land values. These changes were modelled using a new model; which related the percentage change in land values with four variables: the distance from the road; the land use; the land area; and the time that has elapsed since the completion of the roadworks. For a period of 30 years, a comparison was carried out to examine the similarities in the trends of the road users' benefits and the CLVs. Three main periods were found through this comparison. The first period is from year 0 to year 3; the second period is from year 4 after the road's opening to year 19; the last period starts from year 20 and finishes at the end of the analysis. The primary and secondary impacts in the first and the third periods of analysis behaved inversely; while the rest of the analysis period showed similar behaviour for the CLV and the RUCS. It was found that the factors affecting the degree of their similarity were traffic volume and the response of the network users to the new road. In addition, the limitation of the developed model of CLVs in terms of the variables used and particularly in their maximum and minimum values also affects the degree of similarity.

Millions are spent by authorities to maintain and repair the world's potholes. In addition to the direct costs, they can also lead to damaged vehicles and an accelerated deterioration of the road system. The potholes create traffic risks that lead to the daily loss of hundreds of work hours for drivers and passengers. Many road crews are not familiar with the proper materials and methods for pothole repair. Correct selection of pothole patching materials and proper application of repair procedures can greatly increase the longevity of pothole repairs, lead to fewer driver frustrations, and lower road maintenance budgets. The present study aims to develop innovative materials to repair of potholes by using induction heating technology. Three innovative patching materials to repair potholes are proposed, assessed and compared with conventional pothole patching materials. The first material is a combination of a prefabricated asphalt tile and a bonding layer that can be placed into a sanitised pothole and bonded by applying electromagnetic induction heating. The second material involves using prefabricated asphalt pellets to directly fill a pothole and then heated by induction. The third material comprises (1) prefabrication of binder pellets containing bitumen and steel wool that has been coated with a shell to avoid them sticking to each other; (2) the development of a mobile induction heating mixer that can mix the binder pellets with cold aggregate on-site before directly filling a pothole and compacting the mixture. In this research, their tensile and shear strength properties were assessed and demonstrated by repairing simulated potholes on testing slabs and subjected them to wheel tracking tests. The innovative patching materials showed excellent durability higher than a road repaired with cold mix asphalt. Furthermore, the innovative patching materials have been evaluated from economic and environmental standpoints and compared results with conventional hot mix and cold mix. These proposed patching materials have been applied by different raw materials and procedures, and have importance of properties that performed by laboratory tests. Based on the results of loaded wheel test, the service life of each patching materials has been calculated. An inventory was prepared to help quantify the energy requirements, material inputs, and emissions produced during production of raw materials, prefabrication of each product and their final installation. The requisite data was obtained from various sources in the literature. Two maintenance hypothesis were considered. The results showed that three innovative patching materials may be more sustainable and could reduce cost, energy usage and CO2 emissions over time in agreement with hypothesis 1. However, they may cause to increase the economic and environmental impacts over time in agreement with hypothesis 2.

Skid resistance is considered as one of the contributing factors that affect traffic accidents; it is considered as an important property of a road surface that is required to maintain a safe road network. The main aim of this thesis is to establish new skid resistance thresholds for local authority roads. This will be accomplished through the following objectives: 1. to define new site categories based on accident layouts at different network features (e.g. junctions, roundabouts) and the relationships between accidents and geometric characteristics (such as radius of curvature and gradient), 2. to estimate the impact of traffic characteristics (natural logarithm of annual average daily flow, percentage of heavy vehicles, and speed limit); geometric characteristics (radius of curvature, gradient, number of lanes and number of minor accesses); and pavement characteristics (skid resistance, rut depth, and texture depth) on both accident frequency and rate, and 3. To analyse the relation of the expected accident frequencies and rates as a function of skid resistance. This study has included A-road networks for Norfolk, Oxfordshire and Nottinghamshire counties in England, UK. These networks are divided into different site categories these site categories are: 1. non-event; 2. bends (0 - 250) m; 3. bends (250 - 500) m; 4. roundabouts; 5. junctions; 6. gradients. Four different datasets for the period 2005-2010 have been merged to construct the final unique dataset for this study. They are: 1. accident data, 2. traffic data; 3. geometric data; and 4. pavement characteristics data. A series of fixed and random parameters Negative Binomial models have been employed to investigate the effect of skid resistance on accident frequency at different site categories for the three counties. The datasets were modelled by total accidents, by road surface condition (i.e. dry and wet), and by severity level (i.e. fatal and serious or slight). In the same way fixed and random Tobit models have been employed to investigate the effect of skid resistance on accident rate. The model estimation results suggest that skid resistance is negatively associated with the frequency and rate for all accident types at all site categories. A 10% increase in skid resistance leads to a decrease in total, dry, wet, slight, and serious and fatal accident frequencies at network level by 12.24, 10.21, 16.34, 10.68 and 4.92%, respectively. A 10% increase in skid resistance (SCRIM value) leads to a decrease in total, dry, wet, slight, and serious and fatal accident rates at network level by 6.32%, 10.62%, 12.52%, 3.31%, and 4.87%, respectively. This thesis contributes to knowledge in terms of accident prediction approach, showing that application of random parameters modelling as a new approach applied in the UK to estimate accident frequency and rate on A - road networks. This method is introduced as a sufficient approach for the researcher due to the ability to account and correct for heterogeneity, which can arise as a result of several factors relating to the characteristics of traffic, geometric and pavement characteristics. In addition, the random parameters model approach provides a reasonable understanding of the main factors that affect accident frequency and rate. Therefore, this approach allows the researcher to identify and control for confounding factors that may bias estimation. In addition, new skid resistance thresholds for different site categories are established based on the analysis of expected accident frequencies (outputs of random parameters Negative Binomial models); and the analysis of expected accident rates (outputs of random parameters Tobit models) as function of skid resistance.

Age hardening of bitumen is one of the key factors determining the lifetime of an asphalt pavement. When the bitumen is excessively aged, the asphalt mixture will become brittle and its ability of supporting traffic-induced stresses and strains may significantly reduce, which can easily cause some cracking damage to the bound layer of a pavement. As bitumen is always in contact with mineral fillers in asphalt mixtures, the mechanisms of oxidative ageing of binders are significantly influenced by the physical and chemical interaction between fillers and the bitumen. For a long while, attempts to solve the ageing problem of asphalt binder by various methods, including polymer modification, nano-particle enhancement or functional improvement have been undertaken. Hydrated lime is one of many potential additives used in bitumen to improve the performance of asphalt mixtures. Hydrated lime in hot mix asphalt creates multiple benefits. A considerable amount of information exists in the literature on hydrated lime’s ability to control water sensitivity and its well-accepted ability as an anti-stripping agent to inhibit moisture damage. However, recent studies have shown that lime acts as an active filler and anti-oxidant. These properties create multiple benefits for pavements. Although the majority of research on the use of hydrated lime in asphalt mixtures has been carried out in the USA, the beneficial effects of hydrated lime have also been reported worldwide especially in Europe. In the UK, the use of hydrated lime only started in the early 2000’s and still needs a lot of research into its effect on the traditionally used asphalt materials in the UK pavement industry. This research primarily focuses on an in-depth investigation of bitumen ageing mechanisms and evaluation. Furthermore, this research aims to investigate the advantages of using hydrated lime to mitigate ageing in bitumen mastics and asphalts mixtures as a whole. The full project has been broken down into three parts. The first is a pure bitumen study, the second is a mastic level ageing study and the third is a mixture level ageing investigation. The bitumen ageing study investigated the effect of different ageing methods and parameters on bitumen ageing. In addition, this study focused on the mechanisms and factors affecting bitumen ageing and attempted to develop a better understanding of ageing evaluation methods with different perspectives; basic properties, mechanical and rheological behaviour using a dynamic shear rheometer (DSR) and finally a chemical approach with Fourier transform infrared (FTIR). The second level is the mastics level, which investigated the effect of different fillers on bitumen-filler mastic ageing. Particular attention was paid to study the benefits of using hydrated lime on ageing mitigating in the mastic phase. Furthermore, a detailed study at the mastic level was conducted to investigate the effect of hydrated lime on stiffening and ageing mitigation of bitumen mastics. Different means to evaluate this effect were implemented involving both physical and chemical properties. The evaluation testing was aimed at developing a better understanding of hydrated lime anti-oxidant effects on ageing mitigation. Moreover, special attention was paid to the interactions between hydrated lime and bitumen which affects the ageing of bitumen mastics. The third level was the mixture ageing level. In this study, the effect of hydrated lime replacement of the natural aggregate fillers was investigated. This effect on the asphalt mixtures was investigated by different tests on their mechanical properties such as indirect tensile stiffness modulus (ITSM), indirect tensile strength (ITS) and their fracture properties using the semi-circular bending (SCB) test. Furthermore, the effect of ageing on the recovered bitumen was evaluated. The results and conclusions from the performed studies indicate that hydrated lime slows down bitumen ageing more than granite and limestone fillers. This effect depends mainly on the bitumen type and filler concentration. In addition, the research showed that hydrated lime interacts differently with the different bitumens used in this study. This interaction affects stiffening and ageing properties of mastics and mixtures. Furthermore, results show that different ageing indices used in this project correlated well with each other and also with chemical changes. The detailed results from the FTIR tests on recovered fillers and bitumen from the mastics, showed the ability of hydrated lime to adsorb some of the bitumen components such as carboxylic acid products. This mechanism reduces the formation of ageing products and consequently reduces the age hardening of mastics and asphalt mixtures. Unlike hydrated lime, granite filler does not exhibit this ability to react with bitumen.

Most pavements around the world are built with asphalt mixtures. Traditional asphalt mixtures are composed of aggregates and bitumen. Current concern about environmental issues and scarcity of these raw materials has motivated the search for different recycled and renewable resources to be used in pavement engineering. Regarding recycling, the use of Reclaimed Asphalt (RA) materials is nowadays a common and valued practice. However, there still exist some concern about its performance when used in high amounts (>30%) due to its aged state. In terms of renewable resources, the relatively new concept of biobinders (binders manufactured from biomass), as suitable asphalt binder alternatives, is gaining force in pavement engineering. To date, biobinders have shown great potential not only to reduce bitumen demand, but also exhibiting good performance in terms of resisting the main distresses affecting pavements. However, biobinders need in-depth and detailed characterisation in terms of engineering properties before they can be used in practice. The combination of RA and biobinders can be considered as an innovative technique to reduce the consumption of aggregates and bitumen. Within this framework, the main aim of the research described in this thesis was to study the performance of RA mixtures with biobinders at binder and mixture scale in order to gain further understanding of their suitability to be used in actual pavements. For this purpose, biobinders manufactured from pine resin, linseed oil and by-products of the paper industry have been investigated as binders for the total replacement of the virgin bitumen needed in high RA content asphalt mixtures. The research initially focused on the design of the blend of RA binder and biobinders through the study of their conventional and rheological properties which were subsequently used as an input in the design of the asphalt mixtures. Once the design parameters were fixed, the blends of RA binder and biobinders were characterised in terms of their rheological, ageing and adhesion properties, and their performance tested in terms of study rutting, fatigue and thermal cracking resistance. Then, 50% RA mixtures and 70% RA mixtures were characterised for the same properties and the relationships between binder blends and asphalt mixtures were studied. The results showed that the biobinders studied are viscoelastic materials able to efficiently restore some of the properties of the RA binder in an equivalent or better way than conventional bitumens, increasing its viscous component and decreasing its stiffness. The mechanical performance of biobinders and bio-asphalt mixtures regarding rutting, fatigue, thermal cracking and moisture damage was found to be comparable to conventional mixtures. Good relationships were found between the binder blends and asphalt mixtures performance under the assumption of full blending, even though the exact degree of blending remained unknown. In this regard, the blend design performed as the first step was found to satisfactorily work as the input for the design of high RA content asphalt mixtures. Biobinders and bio-asphalt mixtures showed the same ageing tendency as conventional materials although ageing occurred at a faster rate, which can be considered the main drawback of their performance. In the light of the results obtained in this thesis for the materials studied, high RA content asphalt mixtures with biobinders can be considered promising materials to be used in pavement engineering. Full-scale experiments could be the final step for their development.

Harvesting Energy stands as one of the most promising techniques for approaching the global energy problem without depleting natural resources. Pavement solar energy harvesting (PSEH) technology is one of these techniques and it is considered as a new research area and currently under development which aims to enhance pavements for capture, and storage of thermal energy. To advance the study of PSEH, a study was made of the influence of moisture inside asphalt on its energy transport and storage abilities. Measurements of almost all the key thermal properties of asphalt are reported for a range of mixtures with various air void contents ranging from 4.5% to 30%. On the basis of this study it is concluded that, under dry conditions, asphalt mixtures with low air voids content have higher thermo-physical properties (i.e. density, thermal conductivity, specific heat capacity, thermal diffusivity and thermal effusivity) than asphalt mixtures with higher air voids content. Therefore, heating and cooling rates of dense asphalt mixtures were higher than those from porous asphalt mixtures. The total amount of energy accumulated in asphalt mixtures with different air voids content, but with the same constitutive materials, during heating and cooling depends only on the density of the mixtures. In addition, results indicate that asphalt mixtures with high air voids content accumulate less energy than asphalt mixtures with lower air voids content. It is concluded that mixtures with high air voids content are recommended to alleviate the urban heat island effect while mixtures with low air voids content are recommended for harvesting solar heat from pavements. It is concluded that under wet conditions, a relationship exists between the evaporation rate, the heat flux, and the surface temperature during water evaporation. In addition, the evaporation rate has been related to air voids parameters such as air voids content and diameter, tortuosity, or the Euler number. The study also investigated the feasibility of harvesting heat from asphalt concrete mixtures by Thermoelectric Power Generators (TEG) and how the air voids content can affect the recovery of this heat. It was found that increasing and/or maintaining the temperature difference between the hot side and cold side of a TEG is considered to be the most important factor in energy recovery application from asphalt pavement. It is concluded that maintaining the temperature gradient between the asphalt pavement and the subgrade could provide a potential of converting heat energy to electrical energy through the use of Thermoelectric Power generators.

Prediction of pavement performance is important to pavement engineers. Pavement surface deterioration is a dynamic and complicated process. Moisture damage and fatigue are considered as two major causes of pavement deterioration. During a pavement’s service life, the presence of water can lead to loss of stiffness and strength of the asphalt pavement structure. Apart from that, the presence of water can accelerate the propagation and severity of already existing distress. High tensile strain at the bottom of an asphalt layer results fatigue cracking in a pavement. The goal of this research was to develop a series of computational models to predict pavement surface deterioration under the effects of moisture and traffic. The first task was to calculate the pavement surface water pressure under a moving tyre. The water is compressed underneath the tyres, generating a water pressure pulse. This pressure allows surface water to penetrate into the pavement structure. Then the asphalt pavement internal structure (voids distribution) was determined and the water pressure distribution inside the pavement structure was calculated for both fully saturated and partially saturated condition using the surface water pressure. The water pressure expands the voids inside the pavement. Consequently, stress and strain at the edge of the voids, due to frequent traffic passes can lead to failure of the pavement. A ravelling failure probability line was then predicted with the help of cavity expansion theory and asphalt crack propagation law. The case study for the performance of four different asphalt types (HRA, SMA, AC, DBM) using the failure probability calculation shows a good correspondence with their real performance which indicates that this process of predicting failure probability is generally acceptable.